Harman and Blackman here at the NIA have shown that stimulated levels of luteinizing hormone decline with age in the rat pituitary, and Roth, also here, has shown that stimulated levels of prolactin increase in the same system. We will be asking the question whether these age-related hormone changes are reflected in the level of messenger RNA produced by the hormone genes. This will be done by quantitative hybridization analysis of pituitary messenger RNA using cloned hormone gene probes. If message levels are altered, we will proceed to ask whether the changes are at the level of the gene or in the regulatory pathway controlling the gene. This will be done by assaying the expression of a control exogenous hormone gene in the environment of the old and young cell. This analysis should ultimately allow us to pinpoint the defect that aging produces in this regulatory circuit, and may have important implications for the effect of aging on other regulated genes.